As a conventional vehicle auxiliary power supply device, for example, in a vehicle auxiliary power supply device disclosed by Patent Literature 1, a pulse width modulation (PWM) converter is connected to an output terminal of a main transformer that transforms and outputs an AC input supplied from an AC overhead line; and in a configuration in which a three-phase inverter is connected to an output terminal of the PWM converter, a filter circuit that removes a harmonic component included in an output voltage of the three-phase inverter is disclosed.